Tests and diagnosis

After your baby is born, your baby's doctor may suspect tetralogy of Fallot if the baby has blue-tinged skin or if a heart murmur — an abnormal whooshing sound caused by turbulent blood flow — is heard in your child's chest. By using several tests, your doctor can confirm the diagnosis.

Chest X-ray. A typical sign of tetralogy of Fallot on an X-ray is a "boot-shaped" heart, because the right ventricle is enlarged.

Blood test. Your child will need a test that measures the number of each type of cell in the blood, called a complete blood count. In tetralogy of Fallot, the number of red blood cells may be abnormally high (erythrocytosis) as the body attempts to increase the oxygen level in the blood.

Oxygen level measurement (pulse oximetry). This test uses a small sensor that can be placed on a finger or toe to measure the amount of oxygen in the blood.

Echocardiography. Echocardiograms use high-pitched sound waves, inaudible to the human ear, to produce an image of the heart. Sound waves bounce off your baby's heart and produce moving images that can be viewed on a video screen. This test helps diagnose tetralogy of Fallot because it allows the doctor to see whether there is a ventricular septal defect, if the structure of the pulmonary valve is normal, if the right ventricle is functioning properly, and if the aorta is positioned properly.

Electrocardiogram. An electrocardiogram records the electrical activity in the heart each time it contracts. During this procedure, patches with wires (electrodes) are placed on your baby's chest, wrists and ankles. The electrodes measure electrical activity, which is recorded on paper. This test helps determine if your baby's right ventricle is enlarged (ventricular hypertrophy) and if the heart rhythm is regular.

Cardiac catheterization. During this procedure, your doctor inserts a thin flexible tube (catheter) into an artery or vein in your baby's groin and threads it up to his or her heart. A dye is injected through the catheter to make your baby's heart structures visible on X-ray pictures. The catheter also measures pressure and oxygen levels in the chambers of the heart and in the blood vessels.

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